A GPRS BSS is comprised of a Base Transceiver Station including several transceivers (TRX), a Base Station Controller (BSC) and a Packet Control Unit and used for packet service processing and management of packet wireless channel resources at a BSS side.
GPRS is a packet data carrying service and used for discontinuous, burst and frequent data transmission. GPRS provides four different coding modes: CS-1 (9.05 Kbit/s), CS-2 (13.4 Kbit/s), CS-3 (15.6 Kbit/s) and CS-4 (21.4 Kbit/s). Enhanced Data rates for GSM Evolution (EDGE) is an interim scheme from GPRS to the 3rd mobile communication so that existing network operators can provide users with personal multimedia communication services in advance using an existing wireless network device before commercialization of the 3rd mobile network.
EDGE can be regarded as a general radio interface technique providing high bit rate and thus facilitating evolution of a cellular mobile system to functions of the 3rd mobile network.
“High data throughput” of EDGE mainly profits from using an 8 Phase Shift Keying (8PSK) modulation techniques. In conjunction with channel coding schemes with different capacity of error correction, EDGE may provide 9 different modulation coding schemes (MSC), i.e. MCS1 (8.8 Kbit/s), MCS2 (11.2 Kbit/s), MCS3 (14.8 Kbit/s), MCS4 (17.6 Kbit/s), MCS5 (22.4 Kbit/s), MCS6 (29.6 Kbit/s), MCS7 (44.8 Kbit/s), MCS8 (54.4 Kbit/s), MCS9 (59.2 Kbit/s) so as to be adapted to more degraded and wider wireless propagation environment.
EDGE is introduced to provide an enhanced GPRS (E-GPRS) which occupies more Abis (an interface between the base transceiver station and the base station controller) transmission recourses, and it is certainly will result in increasing cost of operators to be provided with additional Abis transmission links.
At present, in order to support EDGE services, a BSS system usually utilizes the following three technical solutions:
Solution one: for TRXs supporting EDGE services, one or more 16 k sub-channels are statically assigned to each Radio Time Slot (RTS), but TRXs of all BTS's on one Abis link can not share 32 64 k Transmission Timeslots (TS's);
Solution two: TRXs of all BTS's on one Abis link may share 32 64 k TS's based on load thereof, but each RTS statically occupies fix bandwidth in the TRX;
Solution three: a portion of 64 k TS's on one Abis link are assigned to a specific BTS and only the TRX on this BTS can share the portion of transmission resources.
As to Solution one, if certain RTS's do not provide EGPRS services, they still occupy statically assigned Abis transmission resources, which results in waste. As to RTS's providing EGPRS services, if they can not achieve MCS9, they can not use statically assigned Abis transmission resources on full load, which also results in waste.
As to Solution two, Abis transmission resources are dynamically assigned based on TRX load to enhance efficiency, but coding mode of each RTS will adjusted in real time in the TRX. Some RTS's degrade from MCS9 to MCS1, but the occupied bandwidth thereof can not be shared with other RTS's, which result in waste of Abis transmission resources. Or, the modulation coding mode (CS1 through CS4, MCS1 through MCS9) is not integral multiple of the minimum assigned unit (usually 16 kbit/s), or data services carried on some RTS's pauses, but the occupied bandwidth thereof can not be shared with other RTS's, which also results in waste of Abis transmission resources.
As to Solution three, if BTS load on an Abis link is low, the occupied Abis resource thereof can not be shared with other BTS's, which also results in waste.